PM gets behind the wheel of the pre-production Chevy Volt and first experiences the car in pure-electric and sustained-charge modes. Here is the full report.

LOS ANGELES--We've been following the Chevy Volt as it has progressed through many milestones before it became a development mule based on the 2011 Chevy Cruze last May. That test drive was completed entirely in electric-only mode. Today, we had a chance to slide behind the wheel of a Volt that looks and feels much closer to production. We experienced the car in both pure-electric and sustained-charge modes, in which the conventional gas engine powers an onboard alternator to supply the needs of the electric motor when the batteries reach an elected state of discharge.

The Volt is still about a year away from production, with an intended launch date of November 2010. But for chief engineer Andrew Farah, the process has been remarkably condensed.

The prototype Volt we drove in the parking lot of the Dodgers Stadium in downtown Los Angeles is what Farah calls a 65 percent write-off vehicle, meaning it's about 65 percent of the way to full production standards. As such, it had a few technical bugs already identified and rectified for future cars. Still, this prototype is a fully representative vehicle in terms of structure and drivetrain.

Electric propulsion systems are well-known for their smooth and quiet operation. So the unobtrusive cycling of a gasoline engine is considered a crucial aspect of this kind of hybrid system. Consumers simply won't tolerate a system that doesn't operate seamlessly. Here is how the Volt performed.

The Specs

The Volt uses a three-phase AC induction motor rated at 120 kilowatts, or 160 hp, powered by a 6-foot-long, 375-pound array of lithium-ion cells mounted low along the Volt's floorpan. Though Farah wouldn't say precisely how much the Volt weighs at this point (we suspect it will tip the scales at around 3500 pounds), he did mention that much work has been done to keep the center of gravity as low as possible, to help diminish the driver's perception of mass. Of course, weight mounted higher in the chassis would result in more noticeable roll.

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The engine is a normally aspirated 1.4-liter inline four-cylinder unit from GM's global Family Zero range, manufactured in Flint, Mich., and it is hooked to a 53-kilowatt alternator to provide current for the Volt's electric motor once the battery pack has discharged about halfway. To prolong battery life the cells are never allowed to recharge higher than about 80 percent of maximum, and they are never permitted to discharge more than about 50 percent unless an emergency occurs, and "limp-home mode" is triggered.

Careful cell management is key to efficient utilization, not to mention the safe operation of lithium-ion cells, some of which have been known to fail in spectacular pyrotechnic fashion unless stringent temperature controls are in place. The Volt has dedicated cooling and heating systems for the battery pack, along with elaborate cell-condition-monitoring mechanisms for optimal efficiency.

The chassis is based on GM's Delta architecture, similar to that underpinning the new Cruze model, which promises contemporary ride and handling performance.

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The Drive

The first few minutes of driving in pure electric mode proved the Volt is exceedingly smooth and quiet in the way it goes down the road. Indeed, the absence of mechanical clamor produces new challenges for noise, vibration and harshness engineers. Farah cited a redesign of a rear-suspension component as an example of issues that arise when the background sounds of a conventional engine and transmission are absent.

That happy state of affairs should last for 40 miles or so on a fully charged battery pack--enough to meet the round-trip commuting requirements of 80 percent of drivers. When the 1.4-liter inline four-cylinder engine cuts in during our drive, Farah is the first to notice it. We're actually surprised to hear the news. That's how subtly the gas engine makes its entrance. And in driving circumstances that only require modest throttle application, most occupants will probably not even notice it.

That's because the job of the gas engine is simply to provide the electric motor with precisely the amount of electrical energy it needs at the time. As Farah points out, if you're on a sustained steep climb and trying to maintain a high cruising speed, the gas engine might climb as high as 5000 rpm to meet the challenge. In that case, the engine's exertions will be very obvious. But most of the time, the small gas engine purrs along at sound levels easily drowned by the car's normal operating noises. Turn on the stereo and you'll likely never hear it kick in.

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In normal operation, the Volt is so quiet that the engineers have incorporated a politely subdued beep into the headlight flasher function to alert pedestrians to its presence. The gas engine will only run when it's called upon to power the electric system. And it seldom needs to rev at a high rpm, since the control computers on board the Volt can vary the alternator load and maintain high efficiency (cranking out plenty of juice) with lower revs.

So why isn't the gas engine used to fully recharge the lithium-ion battery pack back up to its maximum once discharged? It would be an inefficient use of fuel, Farah says, since recharging is what the grid does best, re-energizing the Volt's battery pack in a few hours at 240 volts, and in about 8 hours when suckling at a household 110-volt outlet. Although it's somewhat hard to evaluate the Volt's entire performance envelope within the tight confines of a parking-lot autocross course, it feels adequately powered in its normal mode, which allows a maximum output of about 90 kilowatts (about 121 hp). The Volt is downright peppy in Sport mode, which is selected at a pushbutton on the dash and boosts output by 20 kilowatts (27 hp).

In Sport mode, the front wheels were hard-pressed to stay on-line at full-throttle through one of the coned-off corners on our course. In fact, the outside front tire was even rolling off its rim a bit under the load. During this, the Volt felt stable and predictable. Communication through the steering wheel was direct and pleasantly hefty, and the brake pedal felt similarly deliberate and readable.

Yet another drive mode can be selected at the central-mounted lever--maximum regenerative braking. Drop the selector into Low, intended for slow city use, and the Volt suddenly produces much stronger drag when the throttle is released, producing higher levels of regenerated current. It's so strong that in many urban driving conditions we'd rarely need to touch the brake pedal. The normal regen strategy is adaptable, dictated by running conditions, but it usually produces an effect similar to other hybrids--like a coasting effect on a lifted throttle.

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2011 Chevrolet Volt Photo Gallery

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The Bottom Line

Our brief experience with this Volt prototype in L.A. was impressive. Though the team is still fine-tuning the hardware and software, the Volt appears to be just as livable, comfortable and quick (and in sport mode much more so) as conventional hybrids on the road today. But the real question is: what kind of fuel efficiency will the Volt deliver in the real world? To find out we'll have to slide behind the wheel of a production Volt. We can't wait.

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